Effect of hypoxia on the expression of microRNA in extracellular vesicles of human umbilical cord stem cells in vitro.

Mesenchymal stem cells (MSCs) derived extracellular vesicles, which have been shown to possess therapeutic effects for many diseases. However, how hypoxic conditions would affect exosomal microRNA expression in human umbilical cord MSCs (hUC-MSCs) is currently not investigated. This study aims to investigate the potential function of in vitro microRNAs of hUC-MSC cultured under normoxic and hypoxic conditions. Extracellular vesicles secreted from hUC-MSCs cultured in normoxic (21% O₂) and hypoxic (5% O₂) conditions were collected for microRNA identification. Zeta View Laser Scattering and transmission electron microscopy were used to observe the size and morphology of extracellular vesicles. qRT-PCR was performed to measure the expression of related microRNAs. The Gene Ontology and KEGG pathway were used to predict the function of microRNAs. Finally, the effects of hypoxia on the expression of related mRNAs and cellular activity were examined. This study identified 35 upregulated and 8 downregulated microRNAs in the hypoxia group. We performed target genes analysis to explore the potential function of these microRNA upregulated in the hypoxia group. Significant enrichment of the cell proliferation, pluripotency of stem cells, MAPK, Wnt, and adherens junction pathways were observed in the GO and KEGG pathways. Under hypoxic conditions, the expression levels of 7 target genes were lower than that of the normal environment. In conclusion, this study demonstrated for the first time that microRNA expression in extracellular vesicles of human umbilical vein stem cells cultured under hypoxia is different from that under normal conditions, and these microRNAs may be markers for detecting hypoxia.